package NetWork;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

// 服务器端
public class UdpEchoServer {

    private DatagramSocket socket;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while (true) {
            // 接受请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
            // 根据请求计算响应
            String response = process(request);
            // 把响应写回客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(), 0, response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);

            System.out.printf("[%s:%d] req=%s, resp=%s\n", requestPacket.getAddress(), requestPacket.getPort(),
                    request, response);
        }
    }
    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(15211);
        server.start();
    }
}